Conventional loading docks include an overhead door frame, a dock platform or floor, a recess or pit in the floor, and a dock leveler assembly within the pit to compensate for height differences between a dock platform and the bed of a parked vehicle such as a tractor trailer truck. A dock bumper is typically positioned against the outside dock wall to either side of the pit, extending longitudinally away from the dock floor approximately 4 to 6 inches. The bumpers are engaged by the rear frame or bumper of the vehicle when the vehicle is backed into a parked position relative to the dock leveler assembly. The bumpers prevent the vehicle from striking and damaging the dock wall and the various components of the dock leveler assembly.
Conventional dock bumpers are fabricated from strips of used rubber tires. Others are formed from wood. In one typical construction, the rubber tire strips are cut into sections approximately 24 inches by 6 inches and stacked to a thickness of approximately 18 inches. The stack is sandwiched between steel plates and the plates are bolted so as to compress the strips, thereby forming a bumper assembly. The bumper assembly is oriented so the strips are vertical; 24 inches tall and jutting from the dock wall approximately 6 inches. The steel plates, which usually include an L-bracket, compress the bumper assembly and are then secured to the dock wall using the bracket.
Although a bumper assembly formed from rubber strips or wood can be useful and may be advantageous for certain applications, it suffers from drawbacks. One drawback is that shock loads from the vehicle hitting the bumpers are transferred directly into the dock wall. The steel plates that compress the bumper assembly are secured to the dock wall, typically by several bolts. The stack of rubber strips is adapted to contact the dock wall, when compressed. However, the rubber strips do not completely contact the dock wall and may contact in an uneven manner. In addition, due to the spring rate characteristics of the rubber material, the rubber undergoes only a limited amount of compression, after which higher loads transfer directly to the dock wall. In the case when a trailer hits the bumper hard, the rubber strips absorb a relatively small portion of the load and the remainder is transferred to the dock wall as a shock load. Over time, the repeated shock loads can cause the dock wall to deteriorate, since the wall was not specifically designed to absorb the concentrated point loads.